The mechanism of cell surface recognition and adhesion, and the secondary events triggered by such interactions, will be investigated in Chlamydomonas reinhardi. In the mating reaction of this biflagellate alga, flagellar adhesion between gametes of opposite mating types signals release of a cell wall lysin and activation of mating structures--two events necessary to prepare the gametes for fusion to form a zygote. 1) In combination with several proposed solubilization procedures, two quantitative adhesion assays will be used to detect and purify adhesive molecules. Adhesive and non-adhesive flagellar membranes will be compared by sodium dodecyl sulfate acrylamide gel electrophoresis in combination with isoelectric focusing. These techniques will also be used to determine if flagella which have been inactivated by adhesion and deadhesion have been covalently modified. 2) The mechanism of triggering of cell wall lysin release will be investigated, the lysin enzyme(s) will be isolated and characterized, and the composition of cell walls and their digestion products will be studied. 3) Recently, it was shown that flagellar adhesion involves continual loss and replacement of flagellar adhesion molecules because cells aggregating in cycloheximide (CH) rapidly lose their adhesiveness. The mechanism of this aggregation-induced turnover of adhesion molecules is being investigated by use of 38S pulse-chase experiments, and protease treatment both of aggregating cells and of flagella isolated from aggregating cells.